This invention relates to a fuel injection system for an engine and more particularly to an improved fuel injection system embodying pressure regulation and the layout of the components relative to the engines that facilitate servicing and an improved way of sensing air flow to the engine for controlling the amount of fuel injected.
The use of fuel injection in order to improve engine performance both in the terms of fuel economy and exhaust emission control is gaining wide acceptance. With fuel injection systems, there is provided a high pressure fuel injection which injects fuel into the engine for its combustion. The fuel may be injected either into the induction system or directly into the cylinder. In order to insure adequate and accurate fuel control, it is necessary to insure that the pressure of the fuel supplied to the fuel injectors is maintained at the desired value. In order to accomplish this, it is the normal practice to employ a pressure regulator that regulates the pressure of the fuel supplied to the injector. These pressure regulators normally regulate pressure by dumping excess fuel back to the fuel system so as to maintain the desired pressure at the regulator.
Although this type of regulation obviously is advantageous, there are certain problems in connection with the design of the system. For example, if the regulator regulates by dumping the excess fuel back to the fuel tank, then extremely long conduitries are required. On the other hand, if the regulator dumps the fuel back into the inlet to the fuel pump, then it may be necessary to provide plural fuel filters and complicated piping.
It is, therefore, a principal object to this invention to provide an improved fuel pressure regulating system for the fuel injection system of an internal combustion engine.
It is a further object to this invention to provide a regulating system for a fuel injected engine wherein pressure is regulated by dumping the excess fuel directly back to the fuel filter of the engine, thus eliminating the necessity of multiple filters.
Although fuel injection systems have obvious advantages in more accurate fuel control for the engines, they also require a number of components over and above those of conventional carbureted engines. The layout of these components can provide problems, particularly with many types of applications. For example, in a motorcycle the vehicle is very compact and there is very little space for the positioning of the various components of the fuel injection and engine control systems. In addition to the positioning of the components, it is also desirable to position the components so that individual components requiring servicing can be easily accessed.
It is, therefore, a still further object to this invention to provide an improved arrangement for positioning the various components of a fuel injection and control system that offer ease of access.
It is a specific object to this invention to provide a layout for a fuel injected internal combustion engine wherein the fuel pump and fuel filter may be positioned at one end of the engine and the throttle control and throttle position sensor can be positioned at the other end of the engine.
Two cycle engines offer another application where fuel injection may have particular utility. Because of the porting overlap common with two cycle engines, fuel injection control may be desirable to improve such engine's performance. However, the layout of components for two cycle engines also provides particular challenges.
Frequently, in order to improve the performance of a two cycle engine there is provided one or more valves that control the flow through the exhaust ports so as to control the exhaust port timing. Such exhaust control valves can significantly improve the performance of two cycle engines and accommodate various running conditions. However, the actuating mechanism for such exhaust control valves obviously provides a still further complexity to the engine construction.
It is, therefore, a still further object to this invention to provide an improved layout for a fuel injected, two cycle internal combustion engine and for positioning of the fuel injectors and exhaust control valves so that they can be easily operated and will not interfere with each other.
With two cycle engines, it has been determined that the amount of air flowing to the engine can be accurately and easily measured by measuring the pressure in the crankcase chambers. Such crankcase pressure measurement has a number of advantages in that it avoids the necessity of positioning flow sensors in the induction system which could be damaged or which could interfere with the air flow to the engine.
Crankcase pressure sensors as a means for measuring air flow normally measure the crankcase pressure at a time when the charge is being compressed so as to provide pressure signals that will be indicative of the air inducted into the crankcase chamber. However, there are times when the crankcase chamber is also at a sub-atmospheric pressure and if the pressure sensor is subjected to these sub-atmospheric pressures as well as to high pressures, problems can result.
It is, therefore, a still further object to this invention to provide an improved crankcase pressure sensor control for an injection system for a two cycle engine wherein the pressure sensor is protected from undesirable pressure signals.